In The Journal of American Chemical Society, 125, pp. 2291 (1924), polysilanes were reported to be insoluble in solvents. In recent years, since it was reported in The Journal of American Ceramic Society, 61, pp. 504 that polysilanes are soluble in solvents and films can be made of them, the public attention has been focussed on polysilanes. Japanese Unexamined Patent Publications Sho. 60(1985)-98431 and Sho. 60(1985)-119550 disclose polysilanes which can be dissociated with ultraviolet rays and utilization of them in resists. Further, Physical Review B 35, pp. 2818 (1987) discloses polysilanes having photosemiconductor characteristics in which carriers are mobile due to bonds of their principal chains. These polysilanes are expected to be usable also in electrophotographic photosensitive members. However, in order that polysilane compounds be applicable in electronic materials, those polysilane compounds are required to be such that they are soluble in solvents and capable of providing films which are not accompanied by minute defects and excel in homogeneity. The electronic materials should not be accompanied by any minute defects and because of this, polysilane compounds to be used in the preparation of such electronic materials are required to be high quality polysilane compounds, which can be structurally defined also with respect to substituents and do not cause any abnormality upon film formation.
There have been various reports of the synthesis of polysilane compounds. Those polysilane compounds are still reported to be problematic in using them in electronic materials. In The Journal of American Chemical Society 94(11), pp. 3806 (1972) and Japanese Patent Publication Sho. 63(1988)-38033, there are disclosed low-molecular weight polysilane compounds in with all the Si radicals being substituted by organic groups. Those described in the former literature are of the structure in which the end group of dimethylsilane is substituted by a methyl group. Those described in the latter literature are of the structure in which the end group of dimethylsilane is substituted by an alcoxy group. Any of them is 2 to 6 in degree of polymerization and does not exhibit characteristics as the polymer. Particularly in this respect, none of them has an ability of forming a film as it is, and is therefore, not industrially applicable. High-molecular weight polysilane compounds of the structure in which all the Si radicals are substituted by organic groups have been recently reported in Nikkei New Material, pp. 46, Aug. 15 of 1988. These are synthesized through specific intermediates to cause reduction in their yield and it is difficult to mass-produce these on the industrial scale.
In addition, methods of synthesizing polysilane compounds have been reported by The Journal of Organometallic Chemistry, pp. 198 C27 (1980) and The Journal of Polymer Science, Polymer Chemistry Edition vol. 22, pp. 159-170(1984). However, any of these synthetic methods is directed only to condensation reaction of the polysilane principal chain but does not touch upon the end groups. In any of these synthetic methods, unreacted chlorine radicals and by-products due to side reactions are caused and it is difficult to stably obtain polysilane compounds as desired.
Use of such polysilane compounds as described above as a photoconductive material has been proposed by U.S. Pat. No. 4,618,551, U.S. Pat. No. 4,772,525 and Japanese Unexamined Patent Publication Sho. 62(1987)-269964. However, in any of these cases, occurrence of undesirable negative effects due to said unreacted chlorine radicals and said by-products caused by side reactions are considered.
In U.S. Pat. No. 4,618,551, the foregoing polysilane compounds are used in electrophotographic photosensitive members and an extremely high voltage of 1000 V is applied upon use of those photosensitive members, although a voltage of 500 to 800 V is applied in an ordinary electrophotographic copying machine.
It is considered that this is done in order to prevent occurrence of spotted abnormal phenomena on images reproduced since defects due to the structural defects of the polysilane compound will be caused in the electrophotographic photosensitive member at an ordinary potential. In Japanese Unexamined Patent Publication Sho. 62(1987)-269964, electrophotographic photosensitive members are prepared by using the foregoing polysilane compounds and a photosensitivity is observed for each of them. However, none of those electrophotographic photosensitive members is not sufficient in photosensitivity and is inferior to the known selenium photosensitive member or the known organic photosensitive member in any respect.
There are a number of unsolved problems for any of the known polysilane compounds to be utilized in the electronic materials. Thus, any polysilane compound which can be desirably used for industrial purposes has not yet been realized.